The socket area, which is inside the pelvis, is called the
acetabulum. The ball part of this joint is the top of the leg bone. It
joins with the acetabulum to form the hip joint.

The hip is one of the most stable joints in the body. But, its
function, bearing the body's weight, makes it susceptible to arthritis
due to excessive pressure. Pain in the hip may involve injury to
muscles, tendons, or bursae (small fluid-filled sacs that cushion and
lubricate joints).